A combined artificial neural network, statistical physics, DFT calculations, and experimental study of the adsorption of Rhodamine B dye onto novel polyether sulfone derived laser induced graphene

Rhodamine B (Rh B), a complex organic and persistent dye, poses significant environmental challenges in aquatic ecosystem and human organism health. This study investigates the efficiency of a novel Laser-induced graphene (LIG) fabricated on poly(ether)sulphone (PES) films directly by irradiation with a CO2 laser, for the removal of Rh B dye from aqueous solutions. Several characterisation techniques, including FTIR, SEM, XRD, XPS, Raman spectroscopy, BET surface area and zeta potential analysis were employed. The key parameters of the adsorption such as, pH, temperature, contact time, initial dye concentration and adsorbent dosage, were evaluated and optimised by an artificial neural network model. A comparison of the experimental data with the dye adsorption efficiency predicted by the artificial neural network model showed that this model can estimate the behaviour of the adsorption process of Rh B dye on LIG and FLG (few layer graphene) under different conditions. Under optimal conditions (pH 7.4, 50 mg/L dye concentration, 30 min contact time and 0.5 g/L adsorbent dose), LIG achieved a maximum adsorption capacity of 380.22 mg/g, significantly outperforming FLG (277.77 mg/g). Adsorption followed the pseudo-second-order kinetic model and the equilibrium data were well described by the Langmuir and Freundlich isotherm. Thermodynamic investigations indicated an exothermic, spontaneous adsorption process for LIG. Statistical physics calculations allowed sketching insights into adsorption geometry for Rh B orientation confirming a multi-molecular adsorption mechanism. Theoretical reactivity parameters derived from DFT calculations corroborated experimental findings. These findings demonstrate the potential of LIG as an effective and sustainable solution for Rhodamine B removal from the aqueous system.